A stereoscopic camera is a camera capable of simultaneously acquiring a left-eye image and a right-eye image of a subject using two cameras, and the general stereoscopic camera includes a left-eye camera configured to acquire a left-eye image of a subject and a right-eye camera configured to acquire a right-eye camera of the subject.
FIG. 1 is a schematic view illustrating a stereoscopic camera according to the related art. Referring to FIG. 1, a light beam of a subject 1 passes through a main lens 6. The light beam passing through a half mirror H is imaged on a left-eye camera 4 so that a left-eye image 5 is acquired, and the light beam reflected by the half mirror H is imaged on a right-eye camera 2 so that a right-eye camera 3 is acquired. The images 3 and 5 acquired by the left-eye camera 4 and the right-eye camera 2 have binocular disparity, so that a stereoscopic image may be implemented.
To allow a stereoscopic camera to acquire a stereoscopic image, the right-eye image 3 and the left-eye image 5 should have binocular disparity, and the sizes of the images should be equal to each other. When the sizes of the right-eye image 3 and the left-eye image 5 themselves are not equal to each other, a stereoscopic image having remarkably low quality is obtained.
Thus, to make the sizes of the left-eye image and the right-eye image be equal to each other, the stereoscopic camera according to the related art performs a control such that the sizes of the images are made to be equal to each other by forwards/rearwards moving the left-eye camera 4 along an optical axis (on an X axis), or performs a control such that the sizes of the images are made to be equal to each other by forwards/rearwards moving the right-eye camera 2 along an optical axis. However, a movement of a subject changes from moment to moment. It is practically difficult to capture a stereoscopic image while the left-eye camera and the right-eye camera finely moves forwards/rearwards, and it is very inconvenient to perform a control to change mechanical positions of the cameras.
Further, to acquire a stereoscopic image, the stereoscopic camera should change optical axes of the left-eye camera and the right-eye camera or adjust a convergence angle. In the related art, in case of the left-eye camera 4, an optical axis is changed or the convergence angle is adjusted, by rotating the left-eye camera about a Z axis. The convergence angle is related to a position of a convergence point that is a point at which left and right images of two cameras coincide with each other on a screen when a subject is photographed in a state in which the two cameras or two lenses are spaced apart from each other in a left-right direction by a predetermined distance. By adjusting the convergence point, a stereoscopic image of the subject is viewed to protrude toward the front side of the screen or retract backwards.
To allow the stereoscopic camera to acquire the stereoscopic image, optical axis alignment is necessarily required. The optical axis alignment refers to allowing a position of a half mirror or a camera to coincide with an optical axis by correcting the position of the half mirror or the camera. When optical axes are not aligned with each other, a stereoscopic image having high quality cannot be acquired. Thus, in the related art, to change the optical axes of the left-eye camera and the right-eye camera, in case of the left-eye camera 4, a photographer changes an optical axis by rotating the left-eye camera 4 about a Y axis or changes the optical axis by rotating the left-eye camera 4 about a Z axis.
That is, to acquire a stereoscopic image, the stereoscopic camera according to the related art employs a scheme in which a photographer directly moves a physical position of a camera or rotates the camera.
In Korean Patent No. 1214855 as an example of the related art, adjustment modules are mounted on both a left-eye camera and a right-eye camera, and optical axis alignment and a convergence angle are adjusted using the adjustment modules. However, as described above, Korean Patent No. 1214855 has a problem in that because a structure of the adjustment modules is very complex, applicability to a photographing site in which a subject moving from moment to moment is photographed deteriorates, and costs consumed for commercialization is high.
Further, when a left-eye image and a right-eye image are captured, distances from left and right lenses to a subject should coincide with each other, and physical characteristics of the two lenses should coincide with each other as well. Because there is an error when a lens is manufactured, it is difficult to manufacture lenses having the same physical characteristics. It is very difficult to capture a precise stereoscopic image using two lenses having different physical characteristics. This is because when the two lenses having limitation of physical identity, only if the sizes of the left-eye image and the right-eye image coincide with each other, a stereoscopic image having high quality can be acquired. Thus, a novel monocular stereoscopic camera, which may perform a control to rapidly, easily, and precisely change the sizes of the images, the convergence angle, and the optical axis at a photographing site, is acutely required.